Convert the three value-constraint checkers (built-in, named user type,
and inline type) to located findings so a default/fixed value that is
invalid for its declared type, or an illegal combination of value
constraints, is attached to its declaring element or attribute instead
of the schema root. An editor can underline the offending declaration
by line and column.
Error predicates and reason strings are unchanged; only the location
each finding carries differs. Adds located-diagnostics tests for the
built-in, user-type, and inline-type paths.